The south-west monsoon winds as starts in June and ends in mid September. It is also known as advancing monsoon season or rainy season. During this season, India gets more than 75% of its annual rainfall and more than 90% of the country’s area receives downpour. It is the prime season for Kharif crops.
In the middle of June the direct rays of the Sun fall on tropic of caner due to shift in the position of the Sun from Equator towards northern hemisphere. Therefore, there is an increase in temperature from south to north. The temperature in the main land of India and nearby land masses is high compared to water bodies of the Indian Ocean.
a. The Arabian Sea branch: The Arabian Sea branch of the south-west monsoon strikes the western coast of India in Kerala on the 1st June. Arabian sea winds by carrying more moisture blow along the western coast of India and cause heavy rainfall in the western part of Western Ghats due to obstruction. These winds behave like sea breeze and cause continuous rainfall I the wind ward side of the Western Ghats tHl they lose their moisture.
Agumbe of Karnataka receives the highest rainfall during this season. This regions coming under southeast monsoon winds receive good rainfall wherever they get obstruction by hills and plateaus.
b. The Bay of Bengal branch blow from water bodies towards the Indian mainland due to variation in pressure. These winds carry moisture form the Bay of Bengl and blow along eastern coast and finally reach north eastern hills. In its path, whenever this wind receives obstruction, they cause good rainfall. The eastern part of Eastern Ghats and north astern hills receive heavy rainfall. These winds after crossing eastern coast merge the Arabian sea winds.
The Arabian Sea and the Bay of Bengal winds, after merging, blow towards north eastern regions of India. The shape of the Himalayan Mountains and northeastern hills greatly obstruct these winds. Therefore the Meghalaya plateau region, particularly Nokrek areas of Mawsynram and cheerapunji, receive very high rainfall. This place is popularly called Rainiest or wettest place on the Earth.
The southwest monsoon after crossing northeastern region blow towards east. Since the Himalayas obstruct these winds they have to take westerly direction and blow along the foothills of Himalayas. The shift in the direct 6 sun rays from Tropic of Cancer towards Equator results in the gradual disappearance of southwest monsoons. Indian economy depends on the Monsoons to a large extent.
